Unlock Boss Camos
Animals Camo - Beat Ocelot by reducing his stamina gauge to zero.
Cold War Camo - Defeat Volgin by reducing his stamina gauge to zero.
Fire Camo - Defeat The Fury by reducing his stamina gauge to zero.
Hornet Stripe Camo - Defeat The Pain by reducing his stamina gauge to zero.
Moss Camo - Sneak up on The End and hold him up with a weapon.
Snake Camo - Defeat The Boss by reducing her stamina gauge to zero.
Spider Camo - Defeat The Fear by reducing his stamina gauge to zero.
Spirit Camo - Defeat The Sorrow by reaching the end of the river.

Unlock Guns
Mosin Nagant - Defeat The End by reducing his stamina gauge to zero.
Patriot - Beat the game once
Single Action Army - Select the gun on the right during Snake and Ocelot's final duel.

Figurines In Granin's Office
During the cutscene in Granin's office, use the camera to pan around the room. You'll find figurines of Metal Gear REX, Metal Gear RAY, and Jehuty, which are from the previous Metal Gear Solid and Zone of the Enders games respectively.

Faster Reloading
Some weapons, such as the RPG-7, take a long time to reload. To skip the extra reloading animations, just equip another weapon, and then immediately switch back.

Twirl the Colt Single Action Army
You can twirl it by moving the 3DS system while in FPS aiming mode. This allows you to show off Snake's skill with a revolver and distract Ocelot during your duel with him at Bolshaya Past Crevice. When you're in the open, twirl your revolver and Ocelot will respond with his own revolver tricks and commentary.

Kill The End Early
After walking through the cave and the river at Ponizovje, you'll see a cutscene. As soon as the cutscene ends, equip your SVD sniper rifle and aim it at The End. If you shoot quickly and accurately enough, you can kill The End and skip his boss battle later on. There will be a platoon of soldiers to fight instead.

Skip the Sorrow Battle
During the battle with The Sorrow, immediately lie down in the water. You'll eventually drown, thus prompting the Game Over screen. Instead of choosing the usual options, use the Revival Pill in your inventory; doing so skips the entire fight and allows you to continue the mission.

Escape the Jail Cell Easily
During the part where Snake is locked up in a jail cell, access your radio and set the frequency to 144.75. Doing so automatically unlocks the cell door.